This invention relates generally to liquid level gauging systems, and more particularly to systems employing sets of conducting members adapted to be immersed in a tank in order to provide readings of the level of liquid contained therein.
In the past quite a number of different level gauging devices have been proposed and produced. In many instances of liquid storage, as in the case of oil storage tanks of the type employed on ships, salt water is pumped into the tank so as to displace or remove the oil. Under such circumstances, the oil, being less, dense, floats on the surface of the water, and there is formed a well-defined barrier or border at the interface between the two substances. In certain arrangements heretofore proposed, a float having the proper initial buoyancy was adapted to follow the interface and thus provide an indication of its location at all times. Unfortunately, the tendency of such floats to gather foreign material usually upset the buoyant characteristics of the device thus causing it to sink to the bottom of the tank, after which repairs or other maintenance of the float apparatus were usually required.
Other schemes involving upstanding electrodes which were spaced from one another and adapted to be immersed in the liquid in the tank generally suffered plugging of the gap between them, thus providing erroneous readings and requiring considerable periodic maintenance and trouble shooting. In addition, such arrangements involving the use of conducting electrodes immersed in the liquid being gauged often encountered problems with the corrosive effects of the liquids on the electrodes, particularly where salt water was being used. Under these circumstances, the electrodes tended to deteriorate very rapidly, and undesirable changes in both the physical and electrical characteristics of the electrodes resulted.